Tropical Storm MEGI Advisory 27 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MEGI) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 20W (MEGI), LOCATED APPROXIMATELY 228 NM SOUTHEAST OF
TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A
30-NM RAGGED EYE WITH TIGHTLY-CURVED BANDING WRAPPING INTO THE
LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON
THE EYE IN THE EIR LOOP WHICH LINES UP WELL WITH A LOW REFLECTIVITY
MICROWAVE EYE FEATURE IN THE 261654Z ATMS PASS. THE INITIAL INTENSITY
IS ASSESSED AT 100 KNOTS AND IS BASED ON DVORAK CURRENT INTENSITY
ESTIMATES OF T5.5 FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS INDICATES
EXCELLENT RADIAL OUTFLOW WITH ENHANCED POLEWARD OUTFLOW INTO A
MIDLATITUDE SHORTWAVE TROUGH TO THE NORTH. TY MEGI IS TRACKING WEST-
NORTHWESTWARD ALONG THE PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TY 20W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD,
DRAG THROUGH CENTRAL TAIWAN SHORTLY AFTER TAU 12, THEN CROSS THE
TAIWAN STRAIT BEFORE MAKING A FINAL LANDFALL IN EASTERN CHINA JUST
BEFORE TAU 36. AFTERWARDS, A SECONDARY STR OVER NORTHEASTERN CHINA
WILL ASSUME STEERING AND CAUSE THE CYCLONE TO TRACK ON A FLATTER
WESTWARD TRAJECTORY. A GRADUAL WEAKENING IS EXPECTED OVER THE NEXT 12
HOURS AS INCREASED VERTICAL WIND SHEAR (VWS) ASSOCIATED WITH THE
LEADING EDGE OF THE SECONDARY STR IMPACTS THE SYSTEM. AFTER LANDFALL
INTO TAIWAN, RAPID WEAKENING IS EXPECTED AS LAND INTERACTION,
COMBINED WITH INCREASING VWS, ERODES THE SYSTEM. TY MEGI WILL
EVENTUALLY DISSIPATE INLAND NORTH OF HONG-KONG BY TAU 72. THE DYNAMIC
GUIDANCE REMAINS IN TIGHT AGREEMENT WITH SOME SPREADING AFTER
LANDFALL IN CHINA. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
TRACK FORECAST.//
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